FERTILITY AND STERILITY IN DROSOPHILA 



181 



of life is much shorter than in the controls. In other words, 

 despite all of the unfavorable influences that entered into the 

 crosses in comparison to the controls the point at issue is plainly- 

 evident that the female is producing a large percentage of eggs 

 that are capable of fertilization, the male an abundance of good 

 sperm, and yet when the two meet each other there is incompati- 

 bility of some sort between egg and sperm, as inferred by the num- 

 ber of offspring produced. It is clearly evident that the length of 

 life is a factor, but by no means the only factor, involved in the low 



TABLE 7 

 Control of Woods Hole stock. Brothers and sisters of the high-producing strain used 



in the cross in table 6 



TABLE 8 

 Control of truncate stock. Brothers and sisters of the low-producing strain used in 



the cross in table 6. 



